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Thread: Billet Upper and Lower Made Of 6061 Aluminum?

  1. #21
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    Quote Originally Posted by MistWolf View Post
    7075 aluminum has a harder surface than 6061 Especially when anodized, 7075 has a much harder surface. With 6061, threads are softer which makes them easier to cross thread and will distort at a lower torque. Trigger pin holes will wallow out faster

    While 7075 is harder than 6061, machine tool life is still good When machined before heat treating, aluminum alloys are very easy to machine. Even after heat treating, aluminum is a breeze to machine compared to steel

    7075 is stiffer than 6061 During firing, 7075 will flex less than 6061. 7075 also is less ductile and less prone to bending

    Receivers made of 6061 are billets I do not know of any 6061 receivers that are machined from forgings. Billet receivers cost more and pound for pound are weaker than forged.

    7075 is a better alloy for making forgings Receivers are made from 7075 forgings because they cost less, have greater strength, are more rigid, offer greater durability of threads and trigger pin holes, than any receiver made from 6061, not because of some antiquated material specification

    Buying a receiver made of 6061, especially made from a billet, is paying more for less and makes no sense

    Exactly right. I see no benefit to using the billet receivers on the market that are advertised as "precision" receivers, ever.

    The standard lower and upper forging is fine.
    Last edited by scottryan; 11-15-11 at 15:21.
    "Not every thing on Earth requires an aftermarket upgrade." demigod/markm

  2. #22
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    Quote Originally Posted by Travelingchild View Post
    Seeing as some like to say aircraft grade this or that..

    http://www.aircraftspruce.com/catalo...s/aluminfo.php

    "Aircraft Grade" is buzz term used to decive people.

    Almost all types of aluminum can be called "aircraft grade".

    Most of the lower grade AL is used in non structural applications such as seat mounts, cockpit panels, and other fixtures.
    "Not every thing on Earth requires an aftermarket upgrade." demigod/markm

  3. #23
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    Quote Originally Posted by mrwetwork View Post
    Assuming that the firearms are used exactly as intended there is no issue with 6061. For example... dry firing a complete lower receiver that is made of 7075 will result in almost 0 deformation of the metal between the FCG and the bolt catch. Whereas with 6061 there will be immediate deformation in 10-15 fires. The metal there is only ~.093 thick. Does that affect the performance? No, there is plenty of clearance on both sides and if you dry fire with it in complete rifle configuration the firing pin/bcg limit the hammer from smacking that wall.
    I have to strongly disagree. Dry firing a lower without an upper or dry firing block won't distort a 7075 lower, but it will cause cracks. 7075 is stiffer and very much less ductile than 6061. If you understood the properties of aluminum alloys better, you would see that the difference between 7075 & 6061 do matter in this application. Trigger pin holes and receiver extension threads will last much longer when a lower is made from 7075. Where the receiver extension meets the body of the lower is a stress riser. 7075 will resist deflection better. 6061 will be easier to bend as that's what that alloy was developed for- tighter bends without cracking and weld-ability. Aluminum is a fantastic material but it's critical to choose the right alloy for the job.

    Also, from a production aspect when making these out of billet it costs you roughly 100% more to manufacture from 7075 than 6061. Most companies do not have the coin to make a mold for 7075 forgings.
    Few companies have the dies to forge AR receivers. If I understand it correctly, there are three sources of forgings. (Forgings are made from dies, not molds.) Most companies source the raw forgings from one of these companies and perform their own machining or sub-contract it out. If you check the prices of billeted receivers, you will see they cost more than most of the quality receivers machined from forgings, regardless of alloy type

    My favorite thing about the AR-15 is that most of the parts are not under heavy stress. It is a very smooth system. The upper receiver really is just a housing to allow the bcg to move about. As is the buffer tube. There are no real extreme forces going on there. The most extreme forces are in the chamber, through the gas port and into the gas block where they start bleeding off.
    They may not be under stress from the chamber pressure, as all of that is contained within the barrel, barrel extension and bolt. But the upper does flex during firing and from the weight & leverage of the barrel. A 6061 upper is more likely to permanently distort where it must hold the barrel than one made of 7075. 7075 will also resist battering much better than 6061.

    6061 is a great alloy for what it was developed for. But it offers zero advantages over 7075 for making AR receivers in performance or cost and more disadvantages than you can shake a set of KNS anti-rotation pins at
    Last edited by MistWolf; 11-15-11 at 16:11.
    INSIDE PLAN OF BOX
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  4. #24
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    Quote Originally Posted by scottryan View Post
    "Aircraft Grade" is buzz term used to decive people.

    Almost all types of aluminum can be called "aircraft grade".

    Most of the lower grade AL is used in non structural applications such as seat mounts, cockpit panels, and other fixtures.
    You're correct that "aircraft grade" is nothing more than a buzzword. "Aircraft grade" doesn't mean it's certificated for use in aviation.

    Just a note- While airline seats and flight crew seats are lacking in comfort, their frames and mounts are anything but low grade. We cannot risk having them breaking loose or the seat belts failing and having the seats and people flailing about when the aircraft encounters rough flying conditions
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

    http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/DSC_0114.jpg
    I am American

  5. #25
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    Quote Originally Posted by MistWolf View Post
    I have to strongly disagree. Dry firing a lower without an upper or dry firing block won't distort a 7075 lower, but it will cause cracks.
    We're agreeing here, 6061 will distort. 7075 may crack, but I can't see it happening. I did a test with over 12,000 dry fires on a lower and there was no issues at all.

    Quote Originally Posted by MistWolf View Post
    7075 is stiffer and very much less ductile than 6061. If you understood the properties of aluminum alloys better, you would see that the difference between 7075 & 6061 do matter in this application.
    My point was it is "good enough" and would last under normal use and circumstances. I understand the properties of aluminum plenty.

    Quote Originally Posted by MistWolf View Post
    Trigger pin holes and receiver extension threads will last much longer when a lower is made from 7075. Where the receiver extension meets the body of the lower is a stress riser. 7075 will resist deflection better.
    Again, we are on the same side I am agreeing 7075 is a more suitable material but 6061 can do the job. Not that it is perfect for the job, but can do it.


    Quote Originally Posted by MistWolf View Post
    6061 will be easier to bend as that's what that alloy was developed for- tighter bends without cracking and weld-ability. Aluminum is a fantastic material but it's critical to choose the right alloy for the job.
    Again, see response above.


    Quote Originally Posted by MistWolf View Post
    Few companies have the dies to forge AR receivers. If I understand it correctly, there are three sources of forgings. (Forgings are made from dies, not molds.) Most companies source the raw forgings from one of these companies and perform their own machining or sub-contract it out. If you check the prices of billeted receivers, you will see they cost more than most of the quality receivers machined from forgings, regardless of alloy type
    Yes, I am quite aware that few companies actually do pony up the cash for a die. I also am aware that it is a "die" but for sake of general understanding I replaced it with mold.

    My point was that the pricing structure on a per piece cost basis is as follows in regards to the expense of the raw material used to manufacture the parts.

    In an order of most to least expensive (raw materials):
    7075 Billet
    6061 Billet
    7075 Forged

    Quote Originally Posted by MistWolf View Post
    They may not be under stress from the chamber pressure, as all of that is contained within the barrel, barrel extension and bolt. But the upper does flex during firing and from the weight & leverage of the barrel. A 6061 upper is more likely to permanently distort where it must hold the barrel than one made of 7075. 7075 will also resist battering much better than 6061.
    My point was the stresses are minimal in relative comparison. I personally can not see permanent disfigurement happening to the upper receiver and would be interested to find a way to quantify this.

    Quote Originally Posted by MistWolf View Post
    6061 is a great alloy for what it was developed for. But it offers zero advantages over 7075 for making AR receivers in performance or cost and more disadvantages than you can shake a set of KNS anti-rotation pins at
    Completely agreeing. It can be used, but 7075 is more suitable for the job.

  6. #26
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    Quote Originally Posted by mrwetwork View Post
    ...I personally can not see permanent disfigurement happening to the upper receiver and would be interested to find a way to quantify this...
    I don't know that a 6061 receiver will deform from normal usage, but it will deform easier if or when extraordinary stresses are place on that area. Considering what I see on aircraft, I do not think 6061 is "good enough" for an AR receiver and is the wrong application for the alloy.

    While 6061 may be cheaper to acquire than 7075, the bottom line is the lower receivers that cost the least and are within spec and of good quality are made from 7075 forgings, including (but not limited to) those offered by Aero Precision, LRB, Palmetto and Surplus Ammo & Arms
    Last edited by MistWolf; 11-15-11 at 17:08.
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

    http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/DSC_0114.jpg
    I am American

  7. #27
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    Quote Originally Posted by MistWolf View Post
    While 6061 may be cheaper to acquire than 7075, the bottom line is the lower receivers that cost the least and are within spec are made from 7075 forgings, including (but not limited to) those offered by Aero Precision, LRB, Palmetto and Surplus Ammo & Arms
    Yep, forgings are the best and most affordable. You're just limited to what you can do based on the shape of the forging. So if you want outside the box stuff so to speak it requires use of trickery.

  8. #28
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    That's a good point. I'd love to try the new AX556 billeted ambidextrous lower, but it's more than I can afford at the moment. Matter of fact, it's the only billeted lower I find at all interesting
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

    http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/DSC_0114.jpg
    I am American

  9. #29
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    Thanks for the responses guys. I appreciate it. This debate has, as I feared, devolved into a "7075 billet is a better material for the job" thread. I think we all agree that 7075 is better.

    But....that is like saying that inconel is a better material for a muzzle brake, which it is. But it's not necessarily needed in "most" applications. Other lesser quality materials can be used that provide more than adequate performance.

    The question I'm interested in answering: Is 6061 is a suitable material for this application? Will it's wear properties give good longevity to the system before parts start to fail?

    This thread and others gives me the impression that this question has never really been put to the test. So far I haven't seen anything in this thread or others to prove that 6061 shouldn't be used. The only real data I have found is from a manufacturer of such a system and others who have shot it. So far, all the reports have been favorable.
    Last edited by Clobbersauras; 11-15-11 at 19:20.
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  10. #30
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    Would someone please close this stupid ****ing thread/waste of bandwidth before I beat my head against the wall.

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